determining path to sourced shell script

Question

Is there a way for a sourced shell script to find out the path to itself? I'm mainly concerned with bash, though I have some coworkers who use tcsh.

I'm guessing I may not have a ton of luck here, since sourcing causes commands to be executed in the current shell, so $0 is still the current shell's invocation, not the sourced script. My best thought currently is to do source $script $script, so that the first positional parameter contains the necessary information. Anyone have a better way?

To be clear, I am sourcing the script, not running it:

source foo.bash

Answer 1

In tcsh, $_ at the beginning of the script will contain the location if the file was sourced and $0 contains it if it was run.

#!/bin/tcsh
set sourced=($_)
if ("$sourced" != "") then
    echo "sourced $sourced[2]"
endif
if ("$0" != "tcsh") then
    echo "run $0"
endif

In Bash:

#!/bin/bash
called=$_
[[ $called != $0 ]] && echo "Script is being sourced" || echo "Script is being run"
echo "\$BASH_SOURCE ${BASH_SOURCE[@]}"

Answer 2

I think that you could use $BASH_SOURCE variable. It returns path that was executed:

pbm@tauri ~ $ /home/pbm/a.sh 
/home/pbm/a.sh
pbm@tauri ~ $ ./a.sh
./a.sh
pbm@tauri ~ $ source /home/pbm/a.sh 
/home/pbm/a.sh
pbm@tauri ~ $ source ./a.sh
./a.sh

So in next step we should check if path is relative or not. If it's not relative everything is ok. If it is we could check path with pwd, concatenate with / and $BASH_SOURCE.

Answer 3

For thoroughness and the sake of searchers, here is what these do... It is a community wiki, so feel free to add other shell's equivalents (obviously, $BASH_SOURCE will be different).

test.sh:

#! /bin/sh
called=$_
echo $called
echo $_
echo $0
echo $BASH_SOURCE

test2.sh:

#! /bin/sh
source ./test.sh

Bash:

$./test2.sh
./test2.sh
./test2.sh
./test2.sh
./test.sh
$ sh ./test2.sh
/bin/sh
/bin/sh
./test2.sh
./test.sh

Dash

$./test2.sh
./test2.sh
./test2.sh
./test2.sh

$/bin/sh ./test2.sh
/bin/sh
/bin/sh
./test2.sh

$

Replacing $BASH_SOURCE with $DASH_SOURCE resulted in the same thing.

Answer 4

For the bash shell, I found @Dennis Williamson's answer most helpful, but it didn't work in the case of sudo. This does:

if ( [[ $_ != $0 ]] && [[ $_ != $SHELL ]] ); then
    echo "I'm being sourced!"
    exit 1
fi

Answer 5

Actually, "dirname $0" will get you the path to the script, but you have to interpret it a bit:

$ cat bash0
#!/bin/bash
echo \$0=$0
dirname $0
$ bash0    # "." appears in PATH right now.
$0=./bash0
.
$ ./bash0
$0=./bash0
.
$ $PWD/bash0
$0=/home/00/bediger/src/ksh/bash0
/home/00/bediger/src/ksh
$ $PWD/../ksh/bash0
$0=/home/00/bediger/src/ksh/../ksh/bash0
/home/00/bediger/src/ksh/../ksh
$ ../ksh/bash0
$0=../ksh/bash0
../ksh

You have to prepare to handle "." as the directory name under some common circumstances. I'd experiment a bit, as I remember the dirname built-in to ksh doing things a bit differently when "." appears in PATH.